It's a Raycaster, using 640 1px wide Textures in a ScrollFrame, and a combination of SetPoint/SetSize/SetTexCoords to "draw" the lines.

Nowhere near done - and no real ETA either. I'm working off of a tutorial written in C++, and getting my head around the concept. Once I get that completely figured out, I can move on to more complex things like doing the doors, pushwalls and of course enemy movement. All the other stuff should be fairly simple.